In the field of computers, particularly in the area of servers, disk drive user serviceability is an important factor. The highest form of serviceability involves hot swapping, whereby a drive can be removed and replaced without powering off the unit or taking it offline. Redundant Array of Inexpensive Disks (RAID) level 5 allows any individual failed drive to be removed, and the data stored thereon to be rebuilt on the fly from the remaining disk drives. Historically, server products have used SCSI drives. The connectors used on such SCSI drives require high insertion forces and good mechanical registration, which drove the requirement for a drive tray that incorporated guidance and a camming mechanism to generate the high insertion forces required for properly seating the drive within the enclosure. With the advent of the SATA and SAS connectors, however, drive locational tolerances were relaxed and insertion forces were lowered. This enabled drive mounting without the need for a drive tray mechanism, and ushered in the advent of the tray-less chassis, which offer the customers the advantage of simplified drive replacement.
One requirement that has remained is the need for good mechanical stability of the drive within the chassis. Quite to the contrary, with increasing drive track pitch and areal density, the stability of the mounting is becoming increasingly important. Tray-less designs offer the benefit of improved mounting integrity by virtue of having fewer parts between the chassis and the drive, each of which creates inherent tolerance stack-ups and reduced stiffness. Some prior tray-less designs have incorporated a metal spring into the door of the enclosure to provide some level of axial clamping force on the drive.
Due to the nature of disk drives, as the drive's Voice Coil Motor (VCM) causes the actuator assembly or assemblies within the drive to pivot at high speed, vibrational energy is imparted to the base casting of the disk drive, which is then transferred to the chassis and to the other drives within the enclosure. However, springs, by their very nature, store and release energy imparted to them. Therefore, the vibrational energy generated during the operation of the drive is alternately stored and released by the spring on the door of the chassis of the enclosure, making it more difficult for the enclosed drives to accurately seek and track follow.